Probe Error in Standing-Wave Detectors

Distorted patterns which are observed in standing-wave detectors with deeper probe penetrations are shown to be attributable to reflections at the probe wire. It is demonstrated that the probe, over a wide range of penetrations, acts as a simple shunt admittance across the transmission line. The mathematical and graphical treatment developed on this basis gives a satisfactory account of observed probe patterns, and makes it possible to obtain exact readings even from badly distorted patterns. By applying the results, one is in a position to improve the sensitivity of standing-wave measurements at low-power levels without sacrifice in accuracy, simply by using much deeper probe penetrations.